Studies in patients with idiopathic pulmonary fibrosis have demonstrated: (1) the disease process not only involves parenchyma but also small airways as demonstrated by correlative physiologic and morphologic studies; (2) the best predictor of degree of fibrosis is the drop in the arterial PO2 per unit work done; (3) the majority of patients with idiopathic pulmonary fibrosis develop pulmonary hypertension mid-course in their disease; (4) the degree of parenchymal information can be predicted with the 67Gallium scan; (5) ventilation-profusion studies have demonstrated marked abnormalities in ventilation-profusion ratios; together with mixed venous blood gases this data can be used to predict arterial blood gases within 5%; (6) lavage of the lower respiratory tract demonstrated elevated levels of IgG but normal ratios of T and B cells; (7) lavage fluid analysis have also shown these patients have elevated levels of collagenase, neutral protease and Beta-glucuronidase but not elastase; (8) they have normal phenotype frequencies of HLA-A and B antigens; (9) peripheral lymphocytes from these patients recognize collagen as "non-self"; and (10) an ongoing double-blind study of treatment of this disease with steroids and asothiprine now has 30 patients and should be completed within the next year. BIBLIOGRAPHIC REFERENCES: Reynolds, H.Y., Fulmer, J.D., Kazmierowski, J.A., Roberts, W.C., Frank, M.M., and Crystal, R.G. Analysis of Broncho-Alveolar Lavage Fluid from Patients with Idiopathic Pulmonary Fibrosis and Chronic Hypersenstivity Pneumonitis. J. Clin. Invest., 59, 165-175, 1977. Elson, N.A. and Crystal, R.G. Approaches to the Study of Environmental Pollutants. In: S.D. Lee (ed.). Biological Effects of Environmental Pollutants, Ann Arbor Science Publications, 1977 (in press).